1. Field of the Invention
The present invention relates generally to fluid conveyance using pipes, conduits, and the like, and particularly to a pipeline leak detector employing a drive system for the helical motion of an array of pressure sensing ports along the interior wall of the pipe.
2. Description of the Related Art
Oil and natural gas are likely the two fluids that are first considered when the transport of fluids through pipelines is considered. However, water is a very valuable commodity in many arid parts of the world and water transport via pipelines is a major industry in many areas. Accordingly, considerable research and development has gone into the development of technologies directed to the detection of water leaks in water pipelines. Various principles of leak detection have been developed, including acoustic leak noise correlators and surface listening devices, ground penetrating radar, infrared thermography, and chemical tracing. These methods or principles have a number of limitations when used for the detection of leaks in water distribution networks or pipe systems. The apparatus for these leak detection systems and devices can be quite costly, and their use may be labor intensive and time consuming. Moreover, the results may not be sufficiently accurate and may have noise interference problems in the case of acoustic leak detection systems. All depend at least to some extent upon the material of which the pipe is formed.
Acoustic (noise) detectors are widely used by various municipalities to detect leaks in water lines. Acoustic systems work well in metal pipe, but the effectiveness of acoustic leak detection is questionable with plastic pipe due to high signal attenuation, low frequency content, and the fittings and joints along the pipes affecting acoustic wave propagation. A relatively recent development has been the use of “pigs,” or robotic devices that travel through the interior of the pipeline using pressure differential sensors to detect leaks. These in-pipe mobile sensors, e.g., Sahara® and Smartball®, may overcome many of the shortcomings of conventional acoustic leak detection systems. The desirability of such in-pipe mobile sensors arises from their ability to survey relatively long distances through pipelines in a pipe network, which may be difficult to access using other leak detection techniques.
One limitation of such pressure differential sensors in in-pipe mobile systems is the necessity of placement of the sensors extremely close to the leak, due to the relatively small pressure gradient until very close to the leak. When a sufficient number of detectors is provided, leak detection is less dependent upon pipe material (metal or plastic), pipe depth and soil type, background noise, and perhaps other factors. However, a small leak in a pipe wall may subtend only a small fraction of the internal circumference of the pipe. Accordingly, a large number of pressure sensors are conventionally required in order to cover substantially the entire internal circumference of the pipe as the mobile apparatus travels through the pipe. As an example, a pipe having a diameter of 30 centimeters (cm) would have an internal circumference on the order of 100 cm. A 2 millimeter (mm) diameter leak would require about 50 detectors arranged in a circumferential array about an in-pipe traveling leak detector device for such a pipe, if each of the detectors could cover a lateral span of 1 cm along the pipe wall.
Thus, a pipeline leak detector solving the aforementioned problems is desired.